Number 2 fuel oil is a fraction obtained from petroleum distillation, that is used as heating oil. Number 2 fuel oil can be used interchangeably with diesel fuel. Indeed, both diesel and number 2 fuel oil are typically obtained from the light gas oil cut. The burning of number 2 fuel oil results in well-documented environmental pollution, including significant air pollution by SOX and NOX production and high carbon footprint.
Efforts to find alternative fuels to those derived from petroleum, such as gasoline and diesel fuel, have led to the development of biodiesel fuel. Traditional biodiesel is produced by transesterification of vegetable oils or fats. In such a process, a vegetable fat or oil reacts with an esterifying agent, typically an alcohol, for example methanol or ethanol, with or without a catalyst and with the input of additional energy usually at atmospheric pressure. The time of the reaction can range from 0.5 to 8 hours depending on the temperature.
A common vegetable-oil-derived fuel, typically used as a fuel for diesel engines is referred to as “biodiesel.” Biodiesel is made utilizing the chemical reaction known as transesterification. The process forms two principal products, fatty acid methyl esters (FAME, the chemical name for biodiesel), and glycerin. In this reaction, a vegetable oil or fat reacts with an esterifying agent, usually an alcohol (e.g., methanol or ethanol), with or without a catalyst and with the input of additional energy, normally at atmospheric pressure. The reaction time can vary from about 0.5 to about 8 hours depending on the temperature and whether or not a catalyst is used. A biodiesel fuel generated in this way can be used used in its pure form (in other words without being “diluted” with another fuel, whether a petroleum based fuel or ethanol) or diluted with another fuel, e.g., diesel fuel or gas oil. In its pure form the biodiesel is referred to as B-100; in diluted forms, it is typically identified by the percentage of biodiesel present, e.g., B5, B20, B30, etc.
Burners using a mixture of water and biodiesel in the combustion chamber can produce lower NOx, hydrocarbon, and particulate emissions per unit of power output. The water but acts to lower peak combustion temperatures that result in less NOx formation. Water can be separately injected, but hardware costs are high. Water can also be added to the fuel as an emulsion. However, emulsion stability has historically been a problem.
Therefore, there remains a need for a renewable fuel that is stable, produces reduced emissions, and requires virtually zero infrastructure changes to the boiler.